YES
Input TRS:
      1: is_empty(nil()) -> true()
      2: is_empty(cons(x,l)) -> false()
      3: hd(cons(x,l)) -> x
      4: tl(cons(x,l)) -> l
      5: append(l1,l2) -> ifappend(l1,l2,l1)
      6: ifappend(l1,l2,nil()) -> l2
      7: ifappend(l1,l2,cons(x,l)) -> cons(x,append(l,l2))
Number of strict rules: 7
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #ifappend(l1,l2,cons(x,l)) -> #append(l,l2)
     #2: #append(l1,l2) -> #ifappend(l1,l2,l1)
Number of SCCs: 1, DPs: 2
  SCC { #1 #2 }
POLO(Sum)... succeeded.
      hd	w: 0
      #append	w: x1 + 1
      #is_empty	w: 0
      ifappend	w: 0
      false	w: 0
      true	w: 0
      #tl	w: 0
      append	w: 0
      tl	w: 0
      nil	w: 0
      is_empty	w: 0
      #hd	w: 0
      cons	w: x2 + 2
      #ifappend	w: x3
    USABLE RULES: { }
    Removed DPs: #1 #2
Number of SCCs: 0, DPs: 0